1. Field of the Invention
This invention relates to high speed computers which utilize a central processing unit (CPU) having a large number of printed circuit boards or cards. Each card includes one or more integrated circuit chips as well as discrete wiring and components such as resistors and capacitors. In particular, the present invention relates to the provision of a connection assembly for coupling the printed circuit boards to a main frame within which they are supported.
In a high performance computer, there is always a need to package the electronics in the smallest space possible because shorter lengths of interconnection wire translate into faster speed, i.e., less time to perform a function. Packaging in smaller volumes creates higher interconnection densities on the printed circuit boards. Present interconnection methods are approaching forty contacts per inch on one edge of a printed circuit board. In order to effectively double the contact density, it is desirable to make connections to two opposite edges of the printed circuit board. The printed circuit board is carried in a frame, typically called a "card cage", having two stationary side panels. Connections are made by inserting the printed circuit boards into the card cage and connecting them to connectors carried on the side panels. Because the side panels are stationary, the connectors must be designed so that they do not require panel movement to facilitate connection.
2. Description of the Prior Art
The most common method of connecting opposite edges of a printed circuit board to connectors located on parallel side panels involves the use of "zero insertion force" connectors. Such connectors generally are in the form of a clip which extends over the top and bottom of the printed circuit board and is movable so as to clamp the printed circuit board. When the clip is opened, the printed circuit board can be slid into the proper position for connection. Such connectors are generally quite expensive and are not available in the long lengths which are required for the latest printed circuit boards. In addition, zero insertion force connectors have a relatively large vertical dimension, which prevents the use of a small center to center spacing between printed circuit boards. Furthermore, zero insertion force connectors do not have high enough density to enable them to be used with present high interconnection density printed circuit boards.
Aside from zero insertion force connectors, an expensive method has been developed in which individual connector blocks are connected to the side panels and are actuated with complex cam and sliding mechanisms. Such connectors are quite bulky and in addition create a great deal of stress which causes some deflection of the side panels.